The head of the African Union Commission on Friday congratulated the winner of Nigeria's fiercely fought presidential elections, Bola Tinubu, urging all parties to "uphold peace and the rule of law" following the vote.
In a statement, Moussa Faki Mahamat said that "any post-election dispute or grievance (should) be pursued through the judicial system, as provided for by the law", as opposition parties claimed massive vote-rigging in the February 25 poll.
Faki also commended "the people of Nigeria for demonstrating resilience in their commitment to democratic values by casting their votes for the leaders of their choice."
Almost 25 million people cast their ballots on Saturday in a poll that was largely peaceful but marred by long delays and the slow arrival of online results, angering voters and opposition parties.
Ruling party candidate Tinubu, a former Lagos governor of the ruling All Progressives Congress (APC), was declared winner with 8.8 million votes and the required number of ballots across two-thirds of Nigeria's states.
The ballot pitted Tinubu, 70, against former vice president and main opposition candidate, Peoples Democratic Party (PDP) hopeful Atiku Abubakar, and a surprise third party candidate, Labour Party's Peter Obi, who excited younger voters with his campaign of change.
On Thursday, Obi, a former governor, said he would challenge the outcome of the election in court, claiming he would prove to Nigerians he had won the presidential race.
PDP's candidate Abubakar denounced Tinubu's victory describing it as "rape of democracy" and said he was consulting lawyers to decide on his next steps.
Tinubu, a political kingmaker whose influence earned him the nickname "Godfather of Lagos", is set to succeed two-term President Muhammadu Buhari, who steps down in May.
He faces immense security and economic challenges in Africa's most populous country.